There are many applications where UV light sources are used for treating liquids. The applicant of the present application, Wallenius Water AB in Sweden, has developed and is selling water treatment equipment having a water purifier comprising an elongated tubular treatment chamber with an inlet and an outlet. In the center of the treatment chamber a light generally tubular quartz glass is arranged and inside the quartz glass a UV source, such as a lamp capable of generating wavelengths in the UV region. Low pressure UV lamps offer great efficiency and find particular application e.g. in the disinfection of water. Examples of different types of low pressure lamps include e.g. ozone-free mercury low pressure lamps, mercury ozone-generating low pressure lamps, and U-shaped lamps which supply high power in a compact design.
The inner surface of the treatment chamber of the water treatment equipment may be covered with catalytic material, such as titanium dioxide, which catalysts promotes and increases the amount of treatment material. The treatment equipment also comprises a pumping device which pumps liquid from the tank into the treatment chambers.
One type of treatment reactor developed by the applicant comprises a treatment chamber having oppositely arranged in- and outlets, where the UV light sources are arranged in elongated quartz glass tubes. These tubes are arranged perpendicular to the flow of liquid to be treated through the treatment chamber.
Similar arrangements are also described by others within the field as exemplified by the following.
U.S. Pat. No. 5,625,194 relates to an apparatus for continuous cleaning of tubular lamp wells for UV-light producing lamps.
U.S. Pat. No. 7,425,272 relates to a system for cleaning protective sleeves in UV decontamination systems. The disclosed system for cleaning the outer surface of a quartz sleeve is based on the recognition that providing a honing material with a predetermined abrasiveness through the annulus at high velocity works to remove aggregated particles from the outer surface. In U.S. Pat. No. 7,425,272 the linear velocity of a slurry material passing through the annulus during a cleaning process is about 1 m/s, and in one particular example it is stated that the velocity is at least 0.5 m/s.
Also U.S. Pat. Nos. 5,124,131 and 5,626,768 relate to UV-radiation treatment systems and methods were a liquid is moved along a UV-radiation source.
It is a known problem that air in the liquid which is pumped through the pumping device into the liquid treatment arrangement may badly influence the function of the pump. Today this problem has been solved by different special arrangements, and by taking a number of different actions. For example, nozzles may be arranged at specific locations through which it is possible to withdraw air from the tubing, and from other parts of the system. In addition, the connection tubing must be arranged such that no air is trapped within the tubes.
However, there is still a need in the art for improved liquid treatment apparatuses for purifying liquids which do not suffer from problems associated with malfunctioning of the pump of the apparatus.